The purpose of the present proposal is to strengthen and expand the research program on the biology of neoplasia presently carried out in the Department of Pathology of Temple University School of Medicine. The individual research projects include: (1) a study of the factors that control cellular proliferation in mammalian cells; (2) studies on the mechanism of carcinogenesis; (3) the biology of human and experimental melanoma; (4) studies on gene activity in proliferating and non-proliferating cells; (5) melanogenesis during the cell cycle and nucleo-cytoplasmic interchanges and (6) genetic interactions between tumor and host. An essential part of the proposal includes a number of projects involving collaboration among various investigators inside and outside the Department of Pathology. These studies are described in detail in the Research Plan. The proposed Core Grant would attain these purposes (of expanding and strengthening our research program on the biology of neoplasia) by supporting central facilities for research, to be shared by the investigators involved in this program, and by providing adequate salaries for young investigators. A central theme of this proposal is the application of concepts and techniques of modern cell biology to the study of human neoplastic systems.